The present invention relates to a head supporting device for a universal parallel ruler wherein the head assembly and the scale are floatingly supported from the plane of drawing board.
Devices are well known in which the head of a ruler is upwardly biased by a spring member. With this type of prior art device, however, it becomes more and more difficult to hold the head assembly resting on the drawing board as the inclination of the drawing board increases with respect to the horizontal plane, since the biasing effect of the spring member is at a maximum when the head assembly rests on the drawing board but decreases as the head assembly is displaced in the upward direction.
Accordingly, an object of the present invention is to provide an improved head supporting device for the universal parallel ruler, in which an upward force supporting the head assembly together with the scale increases as the head assembly is displaced in the upward direction together with the scale, with respect to the plane of drawing board and is effectively adjustable in accordance with the inclination of the drawing board with respect to the horizontal position.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.